Which of the following conditions is generally NOT classified as an autoimmune disease of the human body?

Introduction / Context:
Autoimmune diseases occur when the body's immune system mistakenly attacks its own cells and tissues. Many exam questions ask you to identify which diseases are autoimmune and which are not. This question compares several conditions commonly mentioned in health and biology curricula.

Given Data / Assumptions:
- Four conditions are listed: vitiligo, Alzheimer's disease, rheumatoid arthritis, and psoriasis.
- Only one option is primarily not classified as an autoimmune disorder in standard textbooks.
- We assume basic familiarity with the nature of these conditions.

Concept / Approach:
Vitiligo is a condition in which the immune system targets melanocytes, the cells that produce melanin, leading to patches of depigmented skin. Rheumatoid arthritis is a classic autoimmune disease where the immune system attacks the joints. Psoriasis is widely regarded as an immune-mediated or autoimmune skin disease involving overstimulated immune pathways. In contrast, Alzheimer's disease is a neurodegenerative disorder associated with abnormal protein accumulation and nerve cell death in the brain. While the immune system may play a role in inflammation, Alzheimer's is not primarily classified as an autoimmune disease in general science exams.

Step-by-Step Solution:
Step 1: Identify which conditions are explicitly described as autoimmune in science and medical textbooks. Step 2: Recall that rheumatoid arthritis is a classic autoimmune disorder affecting joints. Step 3: Recognize that vitiligo involves the immune system attacking pigment-producing cells in the skin. Step 4: Note that psoriasis is considered an autoimmune or immune-mediated skin disease with chronic inflammation. Step 5: Understand that Alzheimer's disease is primarily a degenerative brain disorder, not categorized as an autoimmune disease in exam contexts.

Verification / Alternative check:
If you check lists of autoimmune diseases in standard references, you will consistently see rheumatoid arthritis, vitiligo, and psoriasis included. Alzheimer's disease, however, appears in lists of neurodegenerative diseases. Although the immune system and inflammation are involved in Alzheimer's, that does not make it an autoimmune disease by definition.

Why Other Options Are Wrong:
Option A: Vitiligo is an autoimmune condition in which immune cells destroy melanocytes, causing depigmented patches of skin.
Option C: Rheumatoid arthritis is a well-known autoimmune disease where the immune system attacks synovial joints, leading to pain and deformation.
Option D: Psoriasis is largely considered an immune-mediated or autoimmune skin disease, characterized by rapid skin cell turnover and inflammation.

Common Pitfalls:
Students sometimes assume that any chronic disease must be autoimmune, which is incorrect. Another error is to pick psoriasis or vitiligo as “cosmetic” problems, forgetting that they have strong immune components. Always remember that Alzheimer's is mainly classified as a neurodegenerative disease, not a classic autoimmune condition.

Final Answer:
The correct answer is Alzheimer's disease, a degenerative brain disorder because it is not primarily classified as an autoimmune disease, whereas vitiligo, rheumatoid arthritis, and psoriasis are all associated with autoimmune mechanisms.